1. Field of the Invention
The present invention relates generally to a heatsink assembly, and more particularly, to a positioning device for connecting a heatsink to a chip set for compact electronic appliances.
2. The Prior Arts
A chip set such as BGA, QFP and CPU used on a computer generates a lot of heat which should be removed from the chip set to keep the optimal operation of the chip set. A conventional heatsink is connected to the chip set and designed to remove the heat from the chip set quickly so as to maintain the chip set to work normally.
Most of the conventional heatsinks for removing the heat from a chip set working at a high speed operation include fins and a fan, the fins absorb the heat and the fan dissipates the heat from the fins.
One of the conventional ways for connecting the heatsink to the chip set is to clip the heatsink to the socket of the chip set by metal clips. However, the conventional metal clips include a complicated structure and require a longer assembly time. The clip tends to reach its fatigue limit quickly. Besides, the chip set can be damaged during processes of installing the clips and the clips might be disengaged from the socket during transportation. Furthermore, if the chip set is directly soldered to the circuit board, there will be no place for the clip to position the heatsink.
Generally, there is a gap about 0.25 mm between the chip set and the circuit board and which is so narrow that no one thinks about using the gap for the heatsink. Some assemblers use heat dissipation tapes to connect the heatsink with the circuit board or directly connect the heatsink to the circuit board by screws. The tapes are easily dried and removed from the surface of the chip set and the screws require holes drilled in the circuit board. There is a limited area on the circuit board so that the holes cannot be drilled in the desired positions. Therefore, most of the manufacturers for making the circuit boards do not drill holes in the circuit boards.
Some manufacturers develop a positioning device that includes a through hole at the center and four side plates extending from four sides of the device. Each side plate includes a hook on an inside thereof. When the heatsink extends through the through hole from the underside of the device, the hooks are hooked to two sides of the chip set, and the heatsink is securely positioned on the chip set.
However, due to manufacturing problems, the hooks might not hook to the sides of the chip set and the heatsink may not have straight or smooth bottom for the heatsink to contact the chip set properly. Therefore, the heat from the chip set cannot be transferred to the heatsink as desired. There are only two side plates hook to two sides of the chip set and the other two side plates are engaged with two slots defined in the heatsink so as to well position the device to the heatsink. The four side plates of the positioning device have the same height so the heatsink has to remove material to form the two grooves through which the side plates of the side plates pass. However, the slots reduce the area for removing the heat from the chip set.
Yet another conventional positioning device for the heatsink includes a rectangular frame and two side plates extend from two opposite sides of the frame, and each side plate has two hooks on an inside thereof. Two positioning rods extend from the other two opposite sides of the frame. A plurality of flexible rods extend from the insides of the frame and each flexible rod has a protrusion on a bottom of a distal end thereof. A plurality of fins of the heatsink extend through the through hole in the center of the frame and hook on the two side plates hook two sides of the chip set. The positioning rods insert through holes defined through the heatsink, and the protrusions on the flexible rods are rested on the heatsink.
Another conventional positioning device includes two hooks on two sides to position the heatsink, and there are two stops on the other sides of the positioning device to prevent the relative movement of the positioning device and the chip set. Nevertheless, the latest electronic products are made to be even more compact and the printed circuit board is made to be smaller than before, while more parts are installed to the small printed circuit board. According to the regulation of JEDC, a 3 mm gap is required between the chip sets so as to avoid interference and over heat. In order to meet the requirement, more and more parts are installed to close to the BGA, which causes the stops mentioned above to push the rectangular frame upward so that the heatsink cannot be in contact with the chip set, and the heatsink is slidable relative to the positioning device.
The present invention provides a positioning device for positioning a heatsink to the chip set and the positioning device is designed to improve the shortcoming of the above mentioned positioning device which pushes the frame upward and causes the heatsink to not be in contact with the chip set, and the heatsink is slidable relative to the positioning device.